Hi benerlandson,
If you are considering online options then the mattress shopping tutorial includes several links to lists of many of the better online options I’m aware of (in the optional online step) that include many different types and categories of mattresses that use different materials and components in a wide range of designs, budgets, firmness levels, and with different return/exchange policies that would be worth considering. I wouldn’t have any “safety” concerns with any of them.
I would also keep in mind that every mattress in the industry contains some type of “chemicals” and that even pure water is a chemical. The real issue that I would focus on is safety which depends on the specific chemicals and the amount of each chemical (safety is dosage related) and the only way to identify any safety issues would be based on the lab testing and certifications for the materials and components in the mattress or the mattress as whole.
Outside of the detailed information in the posts I’ve linked about safety in my previous replies … there is some good information in post #42 here from one of the very knowledgeable members here that would be worth reading as well.
Phoenix